Projection display and illuminating optical system for it

ABSTRACT

An apparatus which makes dark lines due to a central axis of a cross dichroic prism sufficiently inconspicuous. In a second lens array, minute lenses arranged on the same column include three different types of minute lenses having optical axes at different positions. Each row of the minute lenses consists of one of the three types of minute lenses. Partial light fluxes respectively passing through the minute lenses have optical axes at different positions relative to a center of a lighting area of a liquid-crystal light bulb, so as to illuminate different illumination areas.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a projection display apparatus withcolored light combining means and a lighting optical system therefor.

2. Discussion of the Background

A cross dichroic prism is often used for projection display apparatusthat project a color image on a projection screen. For example, in atransmissive liquid-crystal projector, the cross dichroic prism isutilized as colored light combining means that combines three coloredrays of red, green, and blue and emits the composite light in a commondirection. In a reflective liquid-crystal projector, the cross dichroicprism is utilized as colored light separation means that separated abeam of white light into three colored rays of red, green, and blue andalso as colored light combining means that recombines modulated threecolored rays and emits the composite light in a common direction. Aknown example of the projection display apparatus with the crossdichroic prism is disclosed in JAPANESE PATENT LAID-OPEN GAZETTE No.1-302385.

FIG. 17 conceptually illustrates a main part of a projection displayapparatus. The projection display apparatus includes threeliquid-crystal light valves 42, 44, and 46, a cross dichroic prism 48,and a projection lens system 50. The cross dichroic prism 48 combinesthree colored rays of red, green, and blue modulated by the threeliquid-crystal light valves 42, 44, and 46 light and emits the compositelight toward the projection lens system 50. The projection lens system50 focuses the composite light on a projection screen 52.

FIG. 18 is a partly decomposed perspective view illustrating the crossdichroic prism 48. The cross dichroic prism 48 includes four right-angleprisms which are bonded to one another via the respective right-anglesurfaces by an optical adhesive.

FIG. 19 shows a problem arising in the case of utilizing the crossdichroic prism 48. As shown in FIG. 19(A), the cross dichroic prism 48has a red light reflection film 60R and a blue light reflection film 60Bwhich are arranged in a substantially X shape on an X-shaped interfaceformed by the right-angle surfaces of the four right-angle prisms. Thereis an X-shaped layer of optical adhesive 62 formed in the gaps betweenthe four right-angle prisms. Both the reflection films 60R and 60Baccordingly have gaps at a central axis 48a of the cross dichroic prism48.

When a light beam passing through the central axis 48a of the crossdichroic prism 48 is projected on the projection screen 52, a dark linedue to the central axis 48a may be formed in the projected image. FIG.19(B) shows an example of the dark line DL. The dark line DL representsa relatively dark, linear area having a different color from that of theother part and is formed substantially on the center of the projectedimage. It is considered that the dark line DL is ascribed to scatteringof rays and no-reflection of the red light and blue light in the gaps ofthe reflection films in the vicinity of the central axis 48a. A similarproblem arises in a cross dichroic mirror that includes two dichroicmirrors that are arranged in an X shape and respectively have selectivereflection films, such as a red reflection film and a blue reflectionfilm. In this case, a dark line due to a central axis of the mirror isformed in a projected image.

As described above, in the prior-art projection display apparatus, adark line is formed substantially on the center of a projected imagebecause of the central axis of the cross dichroic prism 48 or the crossdichroic mirror.

SUMMARY OF THE INVENTION

The object of the present invention is thus to solve the above problemin the prior art and make a dark line due to a central axis of anoptical means inconspicuous, where the optical means includes twodichroic films arranged substantially in an X shape and may be a crossdichroic prism or a cross dichroic mirror.

The principle for solving the problem is described first with a concreteexample shown in FIGS. 1 through 4. In the drawings, z direction denotesthe direction of the course of light, x direction denotes the directionof 3 o'clock seen from the direction of the course of light (the zdirection), and y direction denotes the direction of 12 o'clock. In thedescription below, the x direction represents the direction of rows andthe y direction represents the direction of columns for the matter ofconvenience. Although the description of the principle is based on aconcrete example for the better understanding, the present invention isnot restricted to this concrete structure in any sense.

In a projection display apparatus, a lighting optical system with twolens arrays each including a plurality of small lenses (hereinafterreferred to as an integrator optical system) as specified in WO94/22042is known as the technique for dividing light from a light source into aplurality of partial light fluxes and thereby reducing an in-planeunevenness of the illuminance of light.

FIG. 1 shows the principle of forming a dark line when an integratoroptical system is adopted in a projection display apparatus with a crossdichroic prism. FIGS. 1(A-1) and 1(B-1) show light fluxes (shown by thesolid lines) passing through a plurality of small lenses 10 which aredifferent in position in the x direction, that is, a plurality of smalllenses 10 existing in different columns, and traces of their centraloptical axes (shown by the fine dotted lines). FIGS. 1(A-2) and 1(B-2)show the positions of dark lines DLa and DLb formed on a screen 7.

A light flux emitted from a light source (not shown) is divided into aplurality of partial light fluxes by first and second lens arrays 1 and2 each including the plurality of small lenses 10. The light fluxespassing through the respective small lenses 10 included in the first andthe second lens arrays 1 and 2 are converted to light fluxes parallel tothe respective central axes of the partial light fluxes by means of aparalleling lens 15. The partial light fluxes passing through theparalleling lens 15 are superposed on a liquid-crystal light valve 3, sothat a predetermined area is uniformly illuminated with the superposedlight fluxes. Although only one liquid-crystal light valve 3 is shown inFIG. 1, the principle of the integrator optical stem and the principleof forming a dark line are also applicable to the her two liquid-crystallight valves.

FIG. 2 is a perspective view illustrating the appearance of the firstand the second lens arrays 1 and 2. Each of the first and the secondlens arrays 1 and 2 includes the small lenses 10 that respectively havea substantially rectangular outline and are arranged in a matrix of Mrows and N columns. In this example, M=10 and N=8. FIG. 1(A-1) shows thetrace of partial light fluxes passing through the small lenses 10 of thesecond column, whereas FIG. 1(B-1) shows the trace of partial lightfluxes passing through the small lenses 10 of the seventh column.

The light fluxes superposed on the liquid-crystal light valve 3 aresubjected to modulation responsive to image information in theliquid-crystal light valve 3 and enter a cross dichroic prism 4. Thelight flux output from the cross dichroic prism 4 is projected on thescreen 7 via a projection lens system 6.

As shown by the rough dotted lines in FIGS. 1(A-1) and 1(B-1), lightfluxes passing through a central axis 5 (along the y direction in thedrawing) of the cross dichroic prism 4 are projected at positions Pa andPb on the screen 7. As discussed previously in the prior art, scatteringof the rays and no-reflection of the light to be reflected in the gapsbetween reflection films in the vicinity of the central axis 5 reducethe quantity of light passing through the vicinity of the central axis5. As shown in FIGS. 1(A-2) and 1(B2), the reduction causes dark linesDLa and DLb, which have the lower luminance than the area aroundluminance on the projection screen 7.

The dark line has the following relation to the first and the secondlens arrays 1 and 2. As clearly shown in FIG. 3(A), which is a partialenlarged view of FIG. 1(A-1), the image formed by the liquid-crystallight valve 3 is inverted and magnified by the projection lens system 6and projected on the projection screen 7. FIG. 3(B) is a cross sectionalview showing an x-y plane including the central axis 5 of the crossdichroic prism 4. Referring to FIGS. 3(A) and 3(B), in case that apartial light flux is cut by the x-y plane including the central axis 5of the cross dichroic prism 4, r1 denotes a distance from one end 11 ofa cross section 8 of the partial light flux to the central axis 5, andr2 denotes a distance from the other end 12 of the cross section 8 ofthe partial light flux to the central axis 5. The image of the crosssection 8 of the partial light flux is inverted and magnified by theprojection lens system 6 and projected on the projection screen 7. Aratio of a distance R2 from one end 13 of a projection area 9 on theprojection screen 7 to the dark line DLa to a distance R1 from the otherend of the projection area 9 to the dark line DLa is accordingly equalto the ratio of r2 to r1. In other words, the position where the darkline DLa is formed depends upon the position where the cross section 8of the partial light flux exists relative to the central axis 5 in thex-y plane including the central axis 5 of the cross dichroic prism 4.

In the examples of FIGS. 1(A-1) and 1(B-1), the partial light fluxeshave cross sections at different positions in the x-y plane includingthe central axis of the cross dichroic prism 4. This means that the darklines DLa and DLb are formed at different positions. In a similarmanner, the partial light fluxes passing through the small lenses 10existing in the columns other than the second column and the seventhcolumn in the first and the second lens arrays 1 and 2 have crosssections at different positions in the x-y plane including the centralaxis 5 of the cross dichroic prism 4. A number of dark linescorresponding to the number of columns included in the first and thesecond lens arrays 1 and 2, N dark lines in this example, are thusformed on the projection screen 7.

The partial light fluxes passing through the M small lenses arranged onthe same column in the first and the second lens arrays 1 and 2 formdark lines DLc at approximately the same position on the projectionscreen 7 as shown in FIG. 4. Each of the N dark lines is formed bysuperposing the partial light fluxes passing through the M small lensesarranged on the same column in the first and the second lens arrays 1and 2. The degree of darkness of each dark line is substantiallyidentical with the summation of the degree of darkness of the dark linesformed by the respective small lenses.

The above description leads to the following principles.

(First Principle)

The first principle is that the different positions of the central axesof the partial light fluxes relative to the central axis 5 of the crossdichroic prism 4 cause dark lines to be formed at different positions.The partial light fluxes passing through the different columns includedin the first and the second lens arrays 1 and 2 are different inposition relative to the central axis 5 of the cross dichroic prism 4and thereby form dark lines at different positions.

(Second Principle)

The second principle is that the different positions of the crosssections of the partial light fluxes in the x-y plane including thecentral axis 5 of the cross dichroic prism 4 are ascribed to thedifference in incident angles of the partial light fluxes entering thecross dichroic prism 4 (see FIG. 1). The partial light fluxes passingthrough the different columns included in the first and the second lensarrays 1 and 2 enter the cross dichroic prism 4 at different incidentangles and thereby have cross sections at different positions relativeto the central axis 5.

Namely different incident angles of the partial light fluxes enteringthe cross dichroic prism 4 or different angles of the partial lightfluxes superposed on the liquid-crystal light valve 3 cause dark linesto be formed at different positions.

(Conclusions)

As discussed previously, the partial light fluxes passing through the Msmall lenses arranged on the same column in the first and the secondlens arrays 1 and 2 respectively form dark lines at substantially thesame position on the projection screen 7. The degree of darkness of eachresulting dark line is substantially equal to the summation of thedegree of darkness of the dark lines formed by the respective smalllenses. A desired arrangement accordingly causes dark lines to be formedat different positions on the projection screen 7 by the respectivepartial light fluxes passing through the M small lenses. Althoughincreasing the total number of dark lines, this arrangement decreasesthe degree of darkness per each dark line, thereby making each dark linesufficiently inconspicuous. It is, however, not required to cause allthe dark lines to be formed at different positions by the respectivepartial light fluxes passing through the M small lenses. One preferableapplication accordingly causes only part of the dark lines to be formedat different positions.

Formation of dark lines at different positions is realized according toeither one of the first principle and the second principle discussedabove.

Based on the first principle, as for part of the partial light fluxespassing through the M small lenses arranged on the same column, thepositions of the central axes of the partial light fluxes relative tothe central axis 5 of the cross dichroic prism 4 should be changed fromthe others.

Based on the second principle, as for part of the partial light fluxespassing through the M small lenses arranged on the same column, theangles of the partial light fluxes superposed on the liquid-crystallight valve 3 or the incident angles of the partial light fluxesentering the cross dichroic prism 4 should be changed from the others.

The present invention has solved the problem of the prior art discussedpreviously according to the above principles. The following describesthe means for solving the problem and its functions and effects.

(Means for Solving the Problems and its Functions and Effects)

The present invention is directed to a lighting optical system foremitting light for use in a projection display apparatus comprising:colored light separation means which separates the light into threecolored rays; three light modulation means which respectively modulatethe three colored rays based on given image signals; colored lightcombining means which has two dichroic films arranged in an X shape anda central axis corresponding to a position where the two dichroic filmscross each other, the colored light combining means combining the threecolored rays respectively modulated by the three light modulation meansto composite light and outputting the composite light in a commondirection; and projection means which projects the composite lightoutput from the colored light combining means on a projection surface,the lighting optical system comprising: a dividing and superposingoptical system that divides a light flux into a plurality of partiallight fluxes, which are arranged in directions of columns and rows, andsuperposes the plurality of partial light fluxes, the columns beingsubstantially parallel to the central axis of the colored lightcombining means, the rows being substantially perpendicular to thedirection of columns, wherein the dividing and superposing opticalsystem is constructed to shift, in the direction of rows, anillumination area on each light modulation means illuminated with partof the partial light fluxes among the partial light fluxes on anidentical column from an illumination area illuminated with the otherpartial light fluxes among the partial light fluxes on the identicalcolumn.

One partial light flux projects the central axis of the colored lightcombining means on the projection surface and forms a dark linecorresponding to the central axis. A plurality of partial light fluxesarranged on one column generally project the central axis of the coloredlight combining means at substantially the same position on theprojection surface and forms a dark line. In the above arrangement, theillumination area on the light modulation means illuminated with part ofthe partial light fluxes is shifted from the illumination areailluminated with the other partial light fluxes in the direction of rows(in the direction virtually perpendicular to the direction of columnssubstantially parallel to the central axis). Based on the firstprinciple discussed above, the position of the central optical paths ofthe part of the partial light fluxes relative to the central axis of thecolored light combining means can be shifted from the position of thecentral optical paths of the other partial light fluxes. This causes thepart of the partial light fluxes and the other partial light fluxes toform dark lines at different positions. This arrangement accordinglymakes the dark lines formed on a projected image sufficientlyinconspicuous.

In accordance with one preferable arrangement of the lighting opticalsystem, the dividing and superposing optical system comprises: a firstlens array having a plurality of small lenses arranged in the directionsof columns and rows; and a second lens array having a plurality of smalllenses respectively arranged corresponding to the plurality of smalllenses of the first lens array, wherein, in the second lens array, atleast part of the small lenses among at least one column of the smalllenses arranged in the direction of columns have optical centersdifferent from optical centers of the other small lenses in the at leastone column.

In this preferable arrangement, among a plurality of small lensesarranged at least on one column, part of the small lenses, which part ofthe partial light fluxes pass through, have optical centers at adifferent position from optical centers of the other small lenses. Thiscauses the optical paths of the part of the partial light fluxes to beshifted from the optical paths of the other partial light fluxes. Basedon the first principle discussed above, this arrangement prevents theplurality of partial light fluxes from projecting the central axis ofthe colored light combining means at substantially the same position.This accordingly makes dark lines formed on a projected imagesufficiently inconspicuous.

In the lighting optical system of this arrangement, it is preferablethat the part of the small lenses are eccentric lenses having opticalcenters at a different position from the position of the optical centersof the other small lenses, in order to cause an illumination area on alighting area by the partial light fluxes passing through the part ofthe small lenses to be shifted in the direction of rows from anillumination area on the lighting area by the partial light fluxespassing through the other small lenses.

This arrangement causes the optical paths of the partial light fluxespassing through the part of the small lenses to be shifted from theoptical paths of the partial light fluxes passing through the othersmall lenses. Based on the first principle discussed above, thisarrangement prevents the plurality of partial light fluxes fromprojecting the central axis of the colored light combining means atsubstantially the same position. This accordingly makes dark linesformed on a projected image sufficiently inconspicuous.

In the lighting optical system of the above arrangement, it ispreferable that a plurality of small lenses located on an identicalcolumn are divided into a plurality of groups, small lenses included inan identical group have optical centers at an identical positionrelative to a lens center, and small lenses included in different groupshave optical centers at different positions relative to the lens center.

In this arrangement, the respective groups have different optical pathsof the partial light fluxes passing through the small lenses. Namely therespective groups form the dark line corresponding to the projectedcentral axis of the colored light combining means at different positionsand prevents the central axis of the colored light combining means frombeing projected at substantially the same position.

It is further preferable that the plurality of small lenses located onan identical column are divided into the plurality of groups so that atotal quantity of light of the partial light fluxes passing through eachof the plurality of groups is equal to each other.

The difference in total quantity of light of the partial light fluxespassing through each group varies the degree of darkness of the darkline corresponding to the central axis of the colored light combiningmeans projected by the partial light fluxes passing through the group.The object of the present invention is to make these dark linessufficiently inconspicuous. The human's eyes have relatively highdiscriminating power based on the relative comparison, and thedifference in degree of darkness among the dark lines is accordinglyundesirable. The identical total quantity of light of the partial lightfluxes passing through each group thus equalizes the degree of darknessof the dark lines formed by the partial light fluxes passing through therespective groups.

The plurality of groups may be at least two sections divided in thedirection of columns. This simple arrangement prevents the central axisof the colored light combining means from being projected atsubstantially the same position.

In one preferable arrangement, the plurality of groups are two sectionsdivided in the direction of columns, optical centers of a plurality ofsmall lenses included in one of the two sections and optical centers ofa plurality of small lenses included in the other of the two sectionsare symmetrical about the lens center.

In this arrangement, the other section includes the same small lenses asthose of one section, which are arranged upside down. Namely the secondlens array consists of only one type of small lenses.

In the lighting optical system of any one of the above arrangement, itis preferable that the plurality of small lenses included in the secondlens array have optical centers that are arranged symmetrically about acenter of the second lens array corresponding to a center of an opticalaxis of a light source.

The light source used in the projection display apparatus generally hasthe largest quantity of light on the center of the optical axis, and thequantity of light decreases with an increase in distance from the centerof the optical axis. In case that such a light source is used in theprojection display apparatus, the above preferable arrangement canequalize the degree of darkness of all the plurality of dark linescorresponding to the central axis of the colored light combining meansprojected by the partial light fluxes passing through the plurality ofsmall lenses included in the second lens array.

In the lighting optical system of any one of the above arrangement, inaccordance with one application, the dividing and superposing opticalsystem further comprises: a superposing lens which superposes andcondenses a plurality of partial light fluxes, which have passed throughthe plurality of small lenses in the first lens array and the pluralityof small lenses in the second lens array, substantially on anilluminating position of each light modulation means; and a polarizingelement interposed between the second lens array and the superposinglens, wherein the polarizing element comprises: a polarization beamsplitter array which has plural sets of a polarization separating filmand a reflecting film that are parallel to each other, the polarizationbeam splitter array separating each of the plurality of partial lightfluxes passing through the plurality of small lenses of the second lensarray into two types of linear polarized light components; and apolarizer which equalizes polarizing directions of the two types oflinear polarized light components separated by the polarization beamsplitter array.

This arrangement converts the light including rays of random polarizedlight to one type of polarized light and thereby enhances theutilization efficiency of light.

The present invention is also directed to a projection display apparatuscomprising: a lighting optical system which emits light; colored lightseparation means which separates the light into three colored rays;three light modulation means which respectively modulate the threecolored rays based on given image signals; colored light combining meanswhich has two dichroic films arranged in an X shape and a central axiscorresponding to a position where the two dichroic films cross eachother, the colored light combining means combining the three coloredrays respectively modulated by the three light modulation means tocomposite light and outputting the composite light in a commondirection; and projection means which projects the composite lightoutput from the colored light combining means on a projection surface,wherein the lighting optical system comprises a dividing and superposingoptical system that divides a light flux into a plurality of partiallight fluxes, which are arranged in directions of columns and rows, andsuperposes the plurality of partial light fluxes, the columns beingsubstantially parallel to the central axis of the colored lightcombining means, the rows being substantially perpendicular to thedirection of columns, and wherein the dividing and superposing opticalsystem is constructed to shift, in the direction of rows, anillumination area on each light modulation means illuminated with partof the partial light fluxes among the partial light fluxes located on asame column from an illumination area illuminated with the other partiallight fluxes among the partial light fluxes located on the identicalcolumn.

Like the respective lighting optical systems described above, theprojection display apparatus including any one of the above lightingoptical systems can make dark lines formed on a projected imagesufficiently inconspicuous.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows the principle of forming a dark line when an integratoroptical system is adopted in a projection display apparatus with a crossdichroic prism;

FIG. 2 is a perspective view illustrating the appearance of first andsecond lens arrays 1 and 2;

FIGS. 3(A) and 3(B) are a partial enlarged view of FIG. 1(A-1) and across sectional view showing an x-y plane including a central axis 5 ofa cross dichroic prism 4;

FIG. 4 conceptually shows the state in which the partial light fluxeswhich have passed through small lenses arranged on an N-th column in thetwo lens arrays 1 and 2 are projected on a projection screen 7;

FIG. 5 is a plan view schematically illustrating a main part of aprojection display apparatus as a first embodiment according to thepresent invention;

FIG. 6 is a perspective view illustrating the appearance of a first lensarray 120;

FIGS. 7(A) and 7(B) show a second lens array 130 in the firstembodiment;

FIGS. 8(A)-8(C) show the function of the second lens array 130;

FIG. 9 conceptually shows the state in which the partial light fluxes bythe first and the second lens arrays 120 and 130 are superposed on aliquid-crystal light valve 252;

FIG. 10 shows the state in which partial light fluxes output from smalllenses 132a, 132b, and 132c pass through a cross dichroic prism 260;

FIGS. 11(A) and 11(B) show the relationship between the position of theoptical axis of the small lens on each row of the second lens array 130and the quantity of light of the partial light flux passing through eachsmall lens;

FIG. 12 shows another second lens array 130' having different structurefrom that of the second lens array 130 shown in FIG. 7;

FIG. 13 illustrates another projection display apparatus as a secondembodiment according to the present invention;

FIGS. 14(A) and 14(B) illustrate structure of a polarizing element 140;

FIG. 15 shows the function of the second lens array 130 in the secondembodiment;

FIG. 16 shows the function of the second lens array 130 in the secondembodiment;

FIG. 17 conceptually illustrates a main part of a projection displayapparatus;

FIG. 18 is a partly decomposed perspective view illustrating a crossdichroic prism 48; and

FIGS. 19(A) and 19(B) show a problem arising in the case of utilizingthe cross dichroic prism 48.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Some modes of carrying out the present invention are described below aspreferred embodiments. In the following description, z direction denotesthe direction of the course of light, x direction denotes the directionof 3 o'clock seen from the direction of the course of light (the zdirection), and y direction denotes the direction of 12 o'clock.

A. First Embodiment

FIG. 5 is a plan view schematically illustrating a main part of aprojection display apparatus as a first embodiment according to thepresent invention. The projection display apparatus includes: a lightingoptical system 100; dichroic mirrors 210 and 212; reflecting mirrors218, 222, and 224; an entrance lens 230; a relay lens 232; three fieldlenses 240, 242, and 244; three liquid-crystal light valves(liquid-crystal panels) 250, 252, and 254; a cross dichroic prism 260;and a projection lens system 270.

The lighting optical system 100 includes: a light source 110 foremitting a substantially parallel light flux; a first lens array 120; asecond lens array 130; a superposing lens 150; and a reflecting mirror160. The lighting optical system 100 is an integrator optical systemthat substantially uniformly causes the three liquid-crystal lightvalves 250, 252, and 254.

The light source 110 has a light-source lamp 112 used as a radiant lightsource for emitting a radiant ray of light and a concave mirror 114 forconverting the radiant ray of light emitted from the light-source lamp112 to a substantially parallel light flux. One preferable example ofthe concave mirror 114 is a parabolic reflector.

FIG. 6 is a perspective view illustrating the appearance of the firstlens array 120. The first lens array 120 includes small lenses 122 whichrespectively have a substantially rectangular shape and are arranged ina matrix of M rows and N columns. In this example, M=6 and N=4. Thesecond lens array 130 includes small lenses that are essentiallyarranged in a matrix of M rows and N columns corresponding to the smalllenses 122 of the first lens array 120. The details of the second lensarray 130 will be described later. The small lenses 122 divide the lightflux emitted from the light source 110 (FIG. 5) into a plurality of(that is, M×N) partial light fluxes and condense the respective partiallight fluxes in the vicinity of the second lens array 130. The contourof each small lens 122 seen from the direction z is set to besubstantially similar to the shape of a display area on theliquid-crystal light valves 250, 252, and 254. In this embodiment, theaspect ratio (the ratio of the lateral dimension to the verticaldimension) of each small lens 122 is set equal to 4 to 3.

In the projection display apparatus shown in FIG. 5, the parallel lightflux emitted from the light source 110 is divided into a plurality ofpartial light fluxes by the first lens array 120 and the second lensarray 130 in the integrator optical system. The partial light fluxesoutput from the respective small lenses 122 of the first lens array 120are condensed by means of the small lenses 122, so that images of thelight source 110 are focused in corresponding small lenses 132 of thesecond lens array 130. Namely a number of secondary light source imagesare formed in the small lenses 132 of the second lens array 130corresponding to the number of small lenses 122 of the first lens array120.

The superposing lens 150 has the function of the superposing opticalsystem that superposes and condenses the partial light fluxes outputfrom the respective small lenses 132 of the second lens array 130 on theliquid-crystal light valves 250, 252, and 254, that is, on the areas tobe illuminated. One lens array having both the function of thesuperposing lens 150 and the function of the respective small lenses ofthe second lens array 130 may be used instead of the two lenses 130 and150. The reflecting mirror 160 has the function of reflecting the lightfluxes output from the superposing lens 150 toward the dichroic mirror210. The reflecting mirror 160 may be omitted from the structureaccording to the requirements. The structure of the embodiment enablesthe respective liquid-crystal light valves 250, 252, and 254 to beilluminated in a substantially uniform manner.

The two dichroic mirrors 210 and 212 have the function of the coloredlight separation means that separates a ray of white light condensed bythe superposing lens 150 into three colored rays of red, green, andblue. The first dichroic mirror 210 transmits a red light component ofthe white light flux emitted from the lighting optical system 100, whilereflecting a blue light component and a green light component. The redlight transmitted by the first dichroic mirror 210 is reflected from thereflecting mirror 218, passes through the field lens 240, and eventuallyreaches the liquid-crystal light valve 250 for red light. The field lens240 converts each partial light flux output from the second lens array130 to a light flux parallel to the central axis of the partial lightflux. The field lenses 242 and 244 arranged before the otherliquid-crystal light valves have the same function. The green lightreflected from the first dichroic mirror 210 is reflected again by thesecond dichroic mirror 212, passes through the field lens 242, andeventually reaches the liquid-crystal light valve 252 for green light.The blue light reflected from the first dichroic mirror 210 istransmitted by the second dichroic mirror 212, passes through the relaylens system including the entrance lens 230, the relay lens 232, and thereflecting mirrors 222 and 224, goes through the field lens 244, andeventually reaches the liquid-crystal light valve 254 for blue light.The relay lens system is used for the blue light component which has thelonger optical path than those of the other colored light components, inorder to prevent a decrease in utilization efficiency of light. In otherwords, the relay lens system enables the partial light fluxes enteringthe entrance lens 230 to be transmitted to the exit lens 244.

The three liquid-crystal light valves 250, 252, and 254 have thefunctions of the light modulation meanss that respectively modulate thethree colored rays responsive to given image information (a given imagesignal) to form images. The cross dichroic prism 260 has the function ofthe colored light combining means that combines the three colored raysand forms a color image. The structure of the dichroic prism 260 isidentical with that described in FIGS. 18 and 19. The cross dichroicprism 260 has a dielectric multi-layered film for reflecting red lightand another dielectric multi-layered film for reflecting blue light thatare arranged in a substantially X shape on an interface of fourright-angle prisms. These dielectric multi-layered films combine thethree colored rays to produce composite light used for projecting acolor image. The composite light generated by the cross dichroic prism260 is output toward the projection lens system 270. The projection lenssystem 270 has the function of the projection optical system thatprojects the composite light on a projection screen 300 to display acolor image.

The projection display apparatus of the first embodiment shown in FIG.is characterized by the second lens array 130. FIG. 7 shows the secondlens array 130 in the first embodiment. The small lenses 132 of thesecond lens array 130 include three different types of small lenses132a, 132b, and 132c having optical axes at different positions. Eachrow of the small lenses 132 consists of one of the three types of smalllenses 132a, 132b, and 132c. Referring to FIG. 7(A), the cross drawn onthe surface of each small lens represents the position of the opticalaxis or the optical center of each small lens. The small lenses 132aconstituting the second and the fifth rows of the second lens array 130have the optical axes on the centers of the respective small lenses132a. The small lenses 132b constituting the third and the sixth rowshave the optical axes shifted in the +x direction from the centers ofthe respective small lenses 132b. The small lenses 132c constituting thefirst and the fourth rows have the optical axes shifted in the -xdirection from the centers of the respective small lenses 132c. FIG.7(B) shows exemplified structures of small lenses having shifted opticalaxes (eccentric lenses), such as the small lenses 132b and 132c. Thesmall lenses 132b and 132c are eccentric lenses that are equivalent tothe lenses having the optical axes shifted from the centers of sphericallenses cut at predetermined positions.

FIG. 8 shows the function of the second lens array 130. FIG. 8(A) is aplan view showing the second row from the top of the second lens array130, FIG. 8(B) is a plan view showing the third row from the top of thesecond lens array 130, and FIG. 8(C) is a plan view showing the fourthrow from the top of the second lens array 130. For the simplicity ofillustration, only the main part on the optical path from the lightsource 110 to the liquid-crystal light valve 252. The followingdescription regards the second column of the first and the second lensarrays 120 and 130 (FIGS. 6 and 7).

Referring to FIG. 8(A), the parallel light flux emitted from the lightsource 110 is divided into a plurality of partial light fluxes by thesmall lenses 122 of the first lens array 120. The partial light flux iscondensed by the small lens 122 to be focused as a light source image inthe small lens 132a of the second lens array 130. The superposing lens150 causes the partial light flux output from the small lens 132a to besuperposed and condensed on a lighting area 252a, which is thelight-entrance surface of the liquid-crystal bulb 252. The small lens132a has the optical axis on the center of the small lens 132a (see FIG.7). The partial light flux output from the small lens 132a accordinglyhas a central axis 256cl that passes through the center of the lightingarea 252a, so that an illumination area 256la is illuminated. Referringto FIG. 8(B), the partial light flux output from the small lens 132b onthe second column of the second lens array 130 is condensed on thelighting area 252a in the same manner as FIG. 8(A). The small lens 132b,however, has the optical axis shifted in the +x direction (see FIG. 7).The partial light flux output from the small lens 132b accordingly has acentral axis 257cl that is shifted in the +x direction from the centerof the lighting area 252a, so that an illumination area 257la, which isshifted in the +x direction from the illumination area 256la, isilluminated. Referring to FIG. 8(C), the partial light flux output fromthe small lens 132c on the second column of the second lens array 130 iscondensed on the lighting area 252a in the same manner as FIGS. 8(A) and8(B). The small lens 132c, however, has the optical axis shifted in the-x direction (see FIG. 7). The partial light flux output from the smalllens 132c accordingly has a central axis 258cl that is shifted in the -xdirection from the center of the lighting area 252a, so that anillumination area 258la, which is shifted in the -x direction from theillumination area 256la, is illuminated. The partial light fluxes on thefifth, the sixth, and the first rows of the second lens array 130respectively have the optical paths identical with those of FIGS. 8(A),8(B), and 8(C). As shown in FIGS. 8(A), 8(B), and 8(C), the partiallight fluxes passing through the small lenses arranged on the samecolumn are superposed on the three different illumination areas 256la,257la, and 258la by the three different types of small lenses 132a,132b, and 132c of the second lens array and the superposing lens 150 toilluminate the lighting area 252a. The respective central axes 256cl,257cl, and 258cl of the partial light fluxes pass through the lightingarea 252a at the different positions relative to the center of thelighting area 252a.

FIG. 9 conceptually shows the state in which the partial light fluxes bythe first and the second lens arrays 120 and 130 are superposed on theliquid-crystal light valve 252. In this drawing, the liquid-crystallight valve 252 is seen from the side of the superposing lens 150. Theillumination area 256la by the partial light fluxes passing through thesmall lenses 132a is shown by the solid line, the illumination area257la by the partial light fluxes passing through the small lenses 132bis shown by the broken line, and the illumination area 258la by thepartial light fluxes passing through the small lenses 132c is shown bythe one-dot chain line. Although the illumination areas 256la, 257la,and 258la have deviations in the y direction in FIG. 9, these deviationsare only for the purpose of clarifying their positional differences. Inthe actual state, there is substantially no deviation in the ydirection. As clearly seen in FIG. 9, the illumination area 257la isshifted in the +x direction from the illumination area 256la, whereasthe illumination area 258la is shifted in the -x direction from theillumination area 256la. The positional difference among theillumination areas 256la, 257la, and 258la in the x direction causes theunevenness of illumination on both ends of the liquid-crystal lightvalve 252. No significant problem, however, arises since an effectivearea 253 actually used for the projection is smaller in size than thecontour of the liquid-crystal light valve 252.

FIG. 10 shows the state in which the partial light fluxes output fromthe small lenses 132a, 132b, and 132c pass through the cross dichroicprism 260. For the better understanding, parts not required fordescription are either omitted or simplified. The central axis 256cl ofthe partial light flux output from the small lens 132a on the second rowand the second column of the second lens array 130, the central axis257cl of the partial light flux output from the small lens 132b on thethird row and the second column, and the central axis 258cl of thepartial light flux output from the small lens 132c on the fourth row andthe second column pass through the cross dichroic prism 260 at differentpositions relative to a central axis 262 of the cross dichroic prism260. As described previously in the first principle, the positionaldifference among the central axes of the partial light fluxes passingthrough the cross dichroic prism 260 relative to the central axis 262 ofthe cross dichroic prism 260 causes dark lines to be formed at differentpositions. This prevents the dark lines formed by the respective partiallight fluxes passing through the M small lenses arranged on the samecolumn from being condensed on one place, and thereby makes the darklines sufficiently inconspicuous.

The following describes the arrangement of small lenses having opticalaxes at different positions in the second lens array 130. FIG. 11 showsthe relationship between the position of the optical axis of the smalllens on each row of the second lens array 130 and the quantity of lightof the partial light flux passing through each small lens. FIG. 11(A)shows a distribution of the quantity of light emitted from the lightsource 110. FIG. 11(B) is a front view showing the second lens array 130from the side of the light source 110. Referring to FIG. 11(A), thelight source 110 generally has the brightest portion in the vicinity ofthe center of the optical axis of the light-source lamp 112, and thebrightness decreases with an increase in distance apart from the centerof the optical axis. When it is assumed that the brightness of thepartial light fluxes passing through the small lenses on the second andthe fifth rows of the second lens array 130 is medium, the brightness onthe third and the fourth rows is greater, whereas the brightness on thefirst and the sixth rows is smaller as shown in FIG. 11(B).

As described previously, among the partial light fluxes passing throughthe M small lenses arranged on the same column of the second lens array130, those passing through the small lenses having optical axes at thesame position form dark lines at the same position on the screen. Inthis embodiment, the set of the small lenses 132c on the first and thefourth rows, the set of the small lenses 132a on the second and thefifth rows, and the set of the small lenses 132b on the third and thesixth rows respectively cause dark lines to be formed at the samepositions on the screen. The difference in total quantity of light amongthe partial light fluxes passing through the respective sets of thesmall lenses leads to the difference in degree of darkness among thethree dark lines formed on the screen. The human's eyes have relativelyhigh discriminating power based on the relative comparison. Thedifference in degree of darkness among a plurality of dark linesaccordingly makes the dark lines rather conspicuous.

The positions of the optical axes of the respective small lenses aredetermined to equalize a total quantity of light of the partial lightfluxes passing through each set of small lenses, which have the opticalaxes at the same position, among the M small lenses arranged on the samecolumn of the second lens array 130. This enables the three dark linesformed by the partial light fluxes passing through the respective setsof small lenses to have the substantially identical degree of darkness.

In this embodiment, the optical axes of the small lenses included in therespective sets, that is, the set of the first and the fourth rows, theset of the second and the fifth rows, and the set of the third and thesixth rows, are arranged at three different positions, in the -xdirection, on the center of the lens, and in the +x direction as shownin FIG. 11(B). This arrangement causes the dark lines formed by thepartial light fluxes passing through the M small lenses arranged on thesame column to be divided into three different places and have theequivalent degree of darkness, thereby making the dark linessufficiently inconspicuous.

The positional shifts of the optical axes of the small lenses 132b and132c may be calculated from the geometrical relations of the second lensarray 130, the superposing lens 150, the field lenses 240, 242, and 244,the liquid-crystal light valves 250, 252, and 254, and the central axis262 of the cross dichroic prism 260, or may be obtained experimentally.It is preferable that the positions of the optical axes of the smalllenses 132b and 132c, that is, the small lenses having the optical axesshifted from the center of the lens, are determined to cause the darklines formed by the partial light fluxes passing through the smalllenses 132b and 132c to exist between the dark lines formed by thepartial light fluxes passing through the small lenses 132a on the secondand the fifth rows, that is, the small lenses having the optical axes onthe center of the lens. The dark lines formed by the partial lightfluxes passing through the small lenses having the optical axes shiftedfrom the center of the lens (the small lenses 132b and 132c) arepreferably to be disposed in the middle of the dark lines formed by thepartial light fluxes passing through the small lenses having the opticalaxes on the center of the lens (the small lenses 132a). This structuremaximizes the interval between the dark lines and prevents the darklines from being overlapped.

In the structure of the embodiment, the position of the optical axis ofthe small lens is changed on each row of the lens array. Anotherstructure may also be applicable as long as the structure prevents thedark lines formed by the partial light fluxes passing through the Msmall lenses arranged on the same column from being converged on oneplace.

FIG. 12 shows another second lens array 130' having different structurefrom that of the second lens array 130 shown in FIG. 7. The second lensarray 130' includes M rows of small lenses that are divided by thecenter of the rows into two sections, an upper section and a lowersection. The upper section consists of small lenses 132'c having opticalaxes shifted in the -x direction from the center of the lens, whereasthe lower section consists of small lenses 132'b having optical axesshifted in the +x direction from the center of the lens. The second lensarray 130' of this structure is applied to the lighting optical system100 shown in FIG. 5 in the projection display apparatus. In this case,the dark lines formed by the partial light fluxes passing through the Msmall lenses arranged on the same column are divided into two differentplaces. Although the second lens array 130' causes the less number ofdivisions of dark lines than the second lens array 130, this structurealso makes the dark lines sufficiently inconspicuous. The second lensarray 130' includes two different types of small lenses with opticalaxes at different positions, which are divided in the direction of rowsinto the two sections, the upper section and the lower section. Thissimple structure enables the second lens array 130' to be manufacturedmore readily than the second lens array 130.

B. Second Embodiment

FIG. 13 illustrates another projection display apparatus as a secondembodiment according to the present invention. The primary difference ofthe second embodiment from the first embodiment is that a lightingoptical system 100' includes a polarizing element 140 interposed betweenthe second lens array 130 and the superposing lens 150. The otherconstituents of the second embodiment are identical with those of thefirst embodiment. The lighting optical system 100' emits predeterminedpolarized light, but there is no difference in main functions. Like thefirst embodiment, the second lens array 130 may be replaced by thesecond lens array 130' shown in FIG. 12. The following describes thefunctions different from those of the first embodiment.

FIG. 14 illustrates structure of the polarizing element 140 (FIG. 13).The polarizing element 140 includes a polarization beam splitter array141 and a selective phase difference plate 142. The polarization beamsplitter array 141 includes a plurality of columnar translucent members143 having a parallelogrammatic cross section, which are bonded to oneanother. Polarization separating films 144 and reflecting films 145 areformed alternately on the interfaces of the translucent members 143. Inorder to enable the polarization separating film 144 and the reflectingfilm 145 to be arranged alternately, the polarization beam splitterarray 141 is manufactured by bonding a plurality of sheet glasses withthese films formed thereon and cutting the bonded sheet glasses slantlyat a predetermined angle.

The light of random polarizing directions passing through the first andthe second lens arrays 120 and 130 is divided by the polarizationseparating film 144 into s-polarized light and p-polarized light. Thep-polarized light passes through the polarization separating film 144,whereas the s-polarized light is reflected by the polarizationseparating film 144 in such a manner that the angle of the incident rayand a perpendicular line at the incident point of the s-polarized lightinto the polarization separating film 144 is symmetrical with the angleof the reflected ray and the perpendicular line (the rule ofreflection). The s-polarized light reflected from the polarizationseparating film 144 is reflected again by the reflecting film 145according to the rule of reflection and is then output to besubstantially parallel to the p-polarized light passing through thepolarization separating film 144. The selective phase difference plate142 is an optical element having λ/2 phase difference layers 146disposed on the light-exit surfaces of the light passing through thepolarization separating films 144. There are no λ/2 phase differencelayers on the light-exit surfaces of the light reflected from thereflecting films 145. The λ/2 phase difference layer 146 accordinglyconverts the p-polarized light transmitted by the polarizationseparating film 144 to s-polarized light. As a result, the light fluxesof random polarizing directions entering the polarizing element 140 aremostly converted to s-polarized light. In accordance with anotherpossible structure, the selective phase difference plate 142 may haveλ/2 phase difference layers 146 disposed on the light-exit surfaces ofthe light reflected from the reflecting films 145 to convert thes-polarized light to p-polarized light.

As clearly shown in FIG. 14(A), the position of the center of thes-polarized light emitted from one polarization separating film 144 ofthe polarizing element 140 (that is, the position of the center when thetwo rays of s-polarized light are regarded as one set of light flux) isdeviated in the x direction from the center of the incident random lightflux (s-polarized light+p-polarized light). The shift is equal to half awidth Wp of the λ/2 phase difference layer 146 (that is, half the widthof the polarization separating film 144 in the x direction). As shown inFIG. 13, the optical axis of the light source 110 (shown by the two-dotchain line) is accordingly shifted from the system optical axis (shownby the one-dot chain line) after the polarizing element 140 by adistance equal to Wp/2.

In the first embodiment (FIG. 5), the partial light flux is condensed byeach small lens 122 of the first lens array 120 to be focused as animage of the light source 110 in the corresponding small lens 132 of thesecond lens array 130. In the second embodiment, on the other hand, itis preferable that a light source image is focused in the vicinity ofthe polarization separating film 144 (FIG. 14) of the polarizing element140, in order to enable the polarizing element 140 to effectivelyutilize each partial light flux output from the second lens array 130.

FIGS. 15 and 16 shows the function of the second lens array 130 (FIG. 7)in the second embodiment. FIG. 15 shows the optical path of the partiallight flux passing through the small lens 132a on the second row and thefirst column of the second lens array 130. FIG. 16 shows the opticalpath of the partial light flux passing through the small lens 132c onthe fourth row and the first column of the second lens array 130.Referring to FIG. 15, a partial light flux 356 that has a central axis356cl parallel to the system optical axis and is output from the smalllens 122 on the second row and the first column of the first lens array120, which is not illustrated here, is condensed by the small lens 122on the polarization separating film 144. A partial light flux 356atransmitted by the polarization separating film 144 is condensed by thesuperposing lens 150 to illuminate the lighting area 252a, which is thelight-entrance surface of the liquid-crystal light valve 252. A partiallight flux 358b reflected from the polarization separating film 144 andfurther from the reflecting film 145 also illuminates the lighting area252a. The small lens 132a has the optical axis on the center of the lens(see FIG. 7). The partial light flux output from the small lens 132aenters the polarizing element 140 in such a manner that the central axis356cl of the partial light flux is parallel to the system optical axis.The two partial light fluxes 356a and 356b output from the polarizingelement 140 illuminate an illumination area 356la in such a manner thatcentral axes 356cla and 356dlb of these partial light fluxes 356a and356b pass through the center of the lighting area 252a.

In the same manner as FIG. 15, referring to FIG. 16, a partial lightflux 358 that has a central axis 358cl parallel to the system opticalaxis and is output from the small lens 122 on the fourth row and thefirst column of the first lens array 120 is condensed by the small lens122 on the polarization separating film 144. A partial light flux 358atransmitted by the polarization separating film 144 is condensed by thesuperposing lens 150 to illuminate the lighting area 252a. A partiallight flux 356b reflected from the polarization separating film 144 andfurther from the reflecting film 145 also illuminates the lighting area252a. The small lens 132c has the optical axis shifted in the -xdirection from the center of the lens (see FIG. 7). The partial lightflux output from the small lens 132c enters the polarizing element 140in such a manner that the central axis 358cl of the partial light fluxis inclined in the direction away from the system optical path relativeto the course of the light. The two partial light fluxes 358a and 358boutput from the polarizing element 140 illuminate an illumination area358la in such a manner that central axes 358cla and 358clb of thesepartial light fluxes 358a and 358b are shifted in the -x direction fromthe center of the lighting area 252a.

Like in the first embodiment, in the second embodiment, the small lenses132a, 132b, and 132c having the optical axes at different positionschange the illuminating position (the superposing position) of thepartial light fluxes output from the small lenses arranged on the samecolumn of the second lens array on the liquid-crystal light valves 250,252, and 254. This structure effectively prevents the dark lines formedby the respective partial light fluxes passing through the M smalllenses arranged on the same column from being concentration on one placeand thereby makes the dark lines sufficiently inconspicuous.

The liquid-crystal light valves 250, 252, and 254 generally havepolarizing planes on their light-entrance surfaces. The liquid-crystallight valves 250, 252, and 254 accordingly modulate only predeterminedpolarized light, whereas the other polarized light is lost as uselesslight fluxes. The structure of the second embodiment causes the lightflux output from the polarizing element 140 to be identical with thepredetermined polarized light utilized in the liquid-crystal lightvalves 250, 252, and 254. Compared with the first embodiment, the secondembodiment thus enhances the utilization efficiency of light in theprojection display apparatus.

Like in the first embodiment, in the second embodiment, the positionalshifts of the optical axes of the small lenses 132b and 132c may becalculated from the geometrical relations of the second lens array 130,the polarizing element 140, the superposing lens 150, the field lenses240, 242, and 244, the liquid-crystal light valves 250, 252, and 254,and the central axis 262 of the cross dichroic prism 260, or may beobtained experimentally. In the second embodiment, the polarizingelement 140 converts part of the partial light flux passing through thesecond lens array to the partial light flux shifted in the direction ofrows by Wp (see FIG. 14). This halves the interval between the partiallight fluxes in the direction of rows. It is accordingly preferable thatthe positions of the optical axes of the small lenses 132b and 132c,that is, the small lenses having the optical axes shifted from thecenter of the lens, are determined to cause the dark lines formed by thepartial light fluxes passing through the small lenses having the opticalaxes shifted from the center of the lens (the small lenses 132b and132c) to be disposed in the middle of the dark lines formed at the 1/2intervals by the partial light fluxes passing through the small lenses132a on the second and the fifth rows, that is, the small lenses havingthe optical axes on the center of the lens.

The present invention is not restricted to the above embodiments ormodes, but there may be many modifications, changes, and alterationswithout departing from the scope or spirit of the main characteristicsof the present invention. Some possible modifications are given below.

In the second lens array, the respective rows or the respective sets ofrows may have optical centers (optical axes) at different positions inthe direction of rows. In another example, only one row or one set ofrows may have the optical axis at a different position. In the aboveembodiments, the light flux from the light source is divided into aplurality of light fluxes arranged in a matrix. The present invention isalso applicable to the case in which the light flux is divided into aplurality of light fluxes at least arranged substantially on the samecolumn. It is accordingly required that at least part of the smalllenses among at least one column of small lenses substantially arrangedin a predetermined direction of columns have the optical center at adifferent position from that of the optical center of the other smalllenses. In this case, the illuminating position (the illumination area)on the lighting area by the partial light fluxes passing through thepart of the small lenses is different from the illuminating position bythe partial light fluxes passing through the other small lenses. Thismakes the position of the partial light fluxes passing through the atleast part of the small lenses relative to the central axis of the crossdichroic prism different from the position of the partial light fluxespassing through the other small lenses and thereby divides the darklines into different positions. This accordingly makes the dark linesformed due to the cross dichroic prism inconspicuous.

The projection display apparatus is accordingly required to have thedividing and superposing optical system that divides a light flux into aplurality of partial light fluxes, which are arranged on at least onecolumn and divided substantially in the direction corresponding to thecentral axis of the colored light combining means, and superposes theplurality of partial light fluxes on the light modulation meanss. Thedividing and superposing optical system may have an illuminatingposition changing means which shifts an optical path regarding part ofthe light fluxes among one column of the partial light fluxes from anoptical path regarding the other partial light fluxes, in order to shiftan illumination area on the light modulation means illuminated with thepart of the light fluxes from an illumination area illuminated with theother partial light fluxes in a direction different from the directioncorresponding to the central axis of the colored light combining means.

All the above embodiments regard the transmission-type projectiondisplay apparatuses. The present invention is, however, also applicableto reflection-type projection display apparatuses. The`transmission-type` implies that the light modulation means, such as theliquid-crystal light valve, transmits light, whereas the`reflection-type` implies that the light modulation means reflectslight. In the reflection-type projection display apparatus, the crossdichroic prism is used both as the colored light separation means whichseparates white light into three colored rays of red, green, and blueand as the colored light combining means which recombines the modulatedthree colored rays and emits the composite light in a predetermineddirection. The reflection-type projection display apparatus to which thepresent invention is applied has similar effects to those of thetransmission-type projection display apparatus.

The lighting optical system of the present invention is applicable to avariety of projection display apparatuses. The projection displayapparatus of the present invention may be used to project and displayimages output from a computer or images output from a video cassetterecorder on a screen.

What is claimed is:
 1. A lighting optical system for emitting light foruse in a projection display apparatus comprising: colored lightseparation means which separates the light into three colored rays;three light modulation means which respectively modulate the threecolored rays based on given image signals; colored light combining meanswhich has two dichroic films arranged in an X shape and a central axiscorresponding to a position where the two dichroic films cross eachother, the colored light combining means combining the three coloredrays respectively modulated by the three light modulation means tocomposite light and outputting the composite light in a commondirection; and a projection means which projects the composite lightoutput from the colored light combining means on a projection surface,the lighting optical system comprising:a dividing and superposingoptical system that divides a light flux into a plurality of partiallight fluxes, which are arranged in directions of columns and rows, andsuperposes the plurality of partial light fluxes, the columns beingsubstantially parallel to the central axis of the colored lightcombining means, the rows being substantially perpendicular to thedirection of columns, wherein the dividing and superposing opticalsystem is constructed to shift, in the direction of rows, anillumination area on each light modulation means illuminated with partof the partial light fluxes among the partial light fluxes on anidentical column from an illumination area illuminated with the otherpartial light fluxes among the partial light fluxes on the identicalcolumn.
 2. A lighting optical system in accordance with claim 1, whereinthe dividing and superposing optical system comprises:a first lens arrayhaving a plurality of small lenses arranged in the directions of columnsand rows; and a second lens array having a plurality of small lensesrespectively arranged corresponding to the plurality of small lenses ofthe first lens array, wherein, in the second lens array, at least partof the small lenses among at least one column of the small lensesarranged in the direction of columns have optical centers different fromoptical centers of the other small lenses in the at least one column. 3.A lighting optical system in accordance with claim 2, wherein the partof the small lenses are eccentric lenses having optical centers at adifferent position from the position of the optical centers of the othersmall lenses, in order to cause an illumination area on a lighting areaby the partial light fluxes passing through the part of the small lensesto be shifted in the direction of rows from an illumination area on thelighting area by the partial light fluxes passing through the othersmall lenses.
 4. A lighting optical system in accordance with claim 2,wherein a plurality of small lenses located on an identical column aredivided into a plurality of groups,small lenses included in an identicalgroup have optical centers at an identical position relative to a lenscenter, and small lenses included in different groups have opticalcenters at different positions relative to the lens center.
 5. Alighting optical system in accordance with claim 4, wherein theplurality of small lenses located on an identical column are dividedinto the plurality of groups so that a total quantity of light of thepartial light fluxes passing through each of the plurality of groups isequal to each other.
 6. A lighting optical system in accordance withclaim 4, wherein the plurality of groups are at least two sectionsdivided in the direction of columns.
 7. A lighting optical system inaccordance with claim 6, wherein the plurality of groups are twosections divided in the direction of columns, andoptical centers of aplurality of small lenses included in one of the two sections andoptical centers of a plurality of small lenses included in the other ofthe two sections are symmetrical about the lens center.
 8. A lightingoptical system in accordance with claim 2, wherein the plurality ofsmall lenses included in the second lens array have optical centers thatare arranged symmetrically about a center of the second lens arraycorresponding to a center of an optical axis of a light source.
 9. Alighting optical system in accordance with claim 2, wherein the dividingand superposing optical system further comprises:a superposing lenswhich superposes and condenses a plurality of partial light fluxes,which have passed through the plurality of small lenses in the firstlens array and the plurality of small lenses in the second lens array,substantially on an illuminating position of each light modulationmeans; and a polarizing element interposed between the second lens arrayand the superposing lens, wherein the polarizing element comprises: apolarizing beam splitter array which has plural sets of a polarizationseparating film and a reflecting film that are parallel to each other,the polarizing beam splitter array separating each of the plurality ofpartial light fluxes passing through the plurality of small lenses ofthe second lens array into two types of linear polarized lightcomponents; and a polarizer which equalizes polarizing directions of thetwo types of linear polarized light components separated by thepolarizing beam splitter array.
 10. A projection display apparatus,comprising:a lighting optical system which emits light; colored lightseparation means which separates the light into three colored rays;three light modulation means which respectively modulate the threecolored rays based on given image signals; colored light combining meanswhich has two dichroic films arranged in an X shape and a central axiscorresponding to a position where the two dichroic films cross eachother, the colored light combining means combining the three coloredrays respectively modulated by the three light modulation means tocomposite light and outputting the composite light in a commondirection; and projection means which projects the composite lightoutput from the colored light combining means on a projection surface,wherein the lighting optical system comprises a dividing and superposingoptical system that divides a light flux into a plurality of partiallight fluxes, which are arranged in directions of columns and rows, andsuperposes the plurality of partial light fluxes, the columns beingsubstantially parallel to the central axis of the colored lightcombining means, the rows being substantially perpendicular to thedirection of columns, and wherein the dividing and superposing opticalsystem is constructed to shift, in the direction of rows, anillumination area on each light modulation means illuminated with partof the partial light fluxes among the partial light fluxes located on asame column from an illumination area illuminated with the other partiallight fluxes among the partial light fluxes located on the identicalcolumn.
 11. A projection display apparatus in accordance with claim 10,wherein the dividing and superposing optical system comprises:a firstlens array having a plurality of small lenses arranged in the directionsof columns and rows; and a second lens array having a plurality of smalllenses respectively arranged corresponding to the plurality of smalllenses of the first lens array, wherein, in the second lens array, atleast part of the small lenses among at least one column of the smalllenses arranged in the direction of columns have optical centersdifferent from optical centers of the other small lenses in the at leastone column.
 12. A projection display apparatus in accordance with claim11, wherein the part of the small lenses are eccentric lenses havingoptical centers at a different position from the position of the opticalcenters of the other small lenses, in order to cause an illuminationarea on a lighting area by the partial light fluxes passing through thepart of the small lenses to be shifted in the direction of rows from anillumination area on the lighting area by the partial light fluxespassing through the other small lenses.
 13. A projection displayapparatus in accordance with claim 11, wherein a plurality of smalllenses located on an identical column are divided into a plurality ofgroups,small lenses included in an identical group have optical centersat an identical position relative to a lens center, and small lensesincluded in different groups have optical centers at different positionsrelative to the lens center.
 14. A projection display apparatus inaccordance with claim 13, wherein the plurality of small lenses locatedon an identical column are divided into the plurality of groups so thata total quantity of light of the partial light fluxes passing througheach of the plurality of groups is equal to each other.
 15. A projectiondisplay apparatus in accordance with claim 13, wherein the plurality ofgroups are at least two sections divided in the direction of columns.16. A projection display apparatus in accordance with claim 15, whereinthe plurality of groups are two sections divided in the direction ofcolumns, andoptical centers of a plurality of small lenses included inone of the two sections and optical centers of a plurality of smalllenses included in the other of the two sections are symmetrical aboutthe lens center.
 17. A projection display apparatus in accordance withclaim 11, wherein the plurality of small lenses included in the secondlens array have optical centers that are arranged symmetrically about acenter of the second lens array corresponding to a center of an opticalaxis of a light source.
 18. A projection display apparatus in accordancewith claim 11, wherein the dividing and superposing optical systemfurther comprises:a superposing lens which superposes and condenses aplurality of partial light fluxes, which have passed through theplurality of small lenses in the first lens array and the plurality ofsmall lenses in the second lens array, substantially on an illuminatingposition of each light modulation means; and a polarizing elementinterposed between the second lens array and the superposing lens,wherein the polarizing element compres: a polarizing beam splitter arraywhich has plural sets of a polarization separating film and a reflectingfilm that are parallel to each other, the polarizing beam splitter arrayseparating each of the plurality of partial light fluxes passing throughthe plurality of small lenses of the second lens array into two types oflinear polarized light components; and a polarizer which equalizespolarizing directions of the two types of linear polarized lightcomponents separated by the polarizing beam splitter array.